Biological tissue substances are imbued with color that is observable under a visible light. The colors of some substances, such as skin, hair and teeth will often differ widely between individuals, and are used as identifying markers to identify the individual to whom the particular tissue sample belongs.
All colored bio-substances will exhibit the color-based functionalities that one might expect, such as a reflection, transmission and refraction of light of various wave lengths.
The colors of biological tissues are often determined by genetic factors. For example, the fact that a particular individual has brown hair rather than blond hair is a reflection of the genetic make-up of the person's parents whose genetic make-up, along with Mendelian chance conspire to cause the person to be a brunette.
Along with being a genetic marker, the color of a particular biological tissue is often reflective of the state of health of either or both of the tissue itself and the organism from which the tissue came. For centuries, healthcare practitioners have observed the colors of body tissues, such as the color of a person's skin, eyes, lips, tongue, fingernails or toenails to determine whether a person has a particular disease condition. For example, the existence of a yellowish coloration of a person's skin is often indicative of diseases or abnormal conditions of the liver and/or gallbladder. Additionally, people also use facial color changes to identify stress, anger, cold, alcohol over indulgence and other health-related conditions.
Modern medical practice often relies on color changes to diagnose and/or monitor conditions. For example, the progress of skin cancer is often monitored through an observation of color changes of areas of abnormal skin, and the development of abnormal moles or pigmentations, that are employed to identify possible growth of cancerous cells.
One of the difficulties with using color identification is that it is difficult to calibrate the colors observed, so that one can easily compare observed colors against either a known standard, or against subsequent observations. Although sophisticated scientific instruments exist that measure color spectrums of material, most of such known medical instruments are expensive and require a special skill to operate. Most color-based tissue matching operations still rely on matching an observed color of a tissue by comparing it to a color chart to find an appropriate match.
Unfortunately, any such match relies to a large extent on the subjective observations of the viewer, along with being the type of observation to which it is very difficult to attach any quantitative measurements. Further, most such color observations are usually done by “hand”, where an observer compares “actual” tissue sample against a particular color chart. As will be discussed below, the difficulties that currently exist in capturing “true color” images make color-based diagnoses that are made from color images (rather than the live tissue), very problematic and unreliable.
For a wide variety of reasons, the color of a tissue sample (or other object) that appears in a photographic image may differ significantly from the actual color (referred to herein as “true color”) of the object.
One factor that will cause the image color to vary from the true color is the influence of the lighting condition that existed when the picture was taken. For example, images captured on film that are taken in a room lighted with a fluorescent light, such as is common in most offices, will tend to have a “colder” or “bluer” appearance, whereas images that are taken wherein the ambient light is provided by Tungsten-based light bulb will tend to have a “warmer” coloration that is more biased toward orange and red hues, rather than blue hues.
Another factor that will cause color to vary in an image captured on film is the manner in which the film is “constructed”. When creating a color film composition, the film manufacturer strives not only to produce a film that reproduces colors accurately, but one that also reproduces colors in an aesthetically pleasing manner. Because purchasing decisions for film are often made by the purchaser based on the user's perceptions of the pleasingness of the colors of the pictures, film manufacturers will often bias their film products to balance the colors away from the “true colors” into more “pleasing” colors. In this regard, some films have a reputation of being “warm” films because their color balance is to bias their color balance in favor of the warmer colors (red and orange), and away from the colder (blue) colors. Other films are known as “colder films”, since their color bias is toward colder, blue colors and away from warmer orange and red colors.
The developing and printing process can also introduce variations in colors. When a film is developed and printed, the technician, or the developer machine will select color balance for a print that may or may not reflect the actual true colors printed. Additionally, factors such as development time, chemical strength, temperature and the like can affect the hue and intensity of the colors shown in the pictures.
The upshot of the foregoing discussion is that it is very difficult, if not almost impossible, to achieve standardized colors when using conventional photography equipment. Since it is very difficult to standardize the color of a particular tissue sample in an image, it is difficult to use an image to analyze the color of the tissue sample to make an accurate diagnosis of the condition of the tissue sample, or more importantly, the condition of the patient from whom the tissue sample was taken.
Further, because of the inconsistency of the way in which colors are reproduced with conventional photograph equipment, it is difficult to track the progress of the condition by tracking changes of the color of a tissue sample shown in the image. It is difficult to track color changes, because a lack of standardization makes it difficult to determine whether a change in the apparent color of a tissue sample has resulted from an actual change in the color of the tissue sample, or rather, resulted from a change in the conditions under which the picture was taken, or a change in which the color was reproduced on the image.
As will be appreciated, those who are employing color to make a diagnosis would prefer to view images wherein the colors of the tissue samples and other contents of the image were standardized, and not subject to change under influence of lighting, development and the like.
To a large extent today, digital photography is replacing traditional film photography as the medium of choice for many photographic applications. Rather than capturing a picture on a film substrate, the image is captured on solid state sensors such as charge coupled devices (CCDs). CCDs consist of integrated circuits that contain an array of linked or coupled light sensitive capacitors. It is also known as a “color capture device”. CCDs are often made from C-MOS devices that are complimentary metal-oxides semi-conductors.
Unfortunately, these CCD chips currently in use are not inherently better than film in capturing “true color”. One reason that the CCD chips are no better than film is that CCD chips, when capturing an image, are still subject to the vagaries induced by the ambient light in which the image is being captured. Additionally, variations in color from “true color” can be introduced by camera components such as the camera lens materials, coatings used on lenses and the like. Further, the image captured by the CCDs of commercially available cameras usually undergo color “processing” by the cameras. The color processing by such cameras consists of these color images being processed by the software within the camera. Because most cameras are intended for the photographic and graphic arts markets, the camera companies have found that their digital camera products are better received when the output of the image captured by the CCD of the camera is processed so that the colors of the image are balanced and processed to look natural and be vivid and pleasing to the human eyes. As such, the cameras are designed to color bias the image to enhance the beauty of the picture, rather than to adjust the colors of the picture to reflect the true colors of the image. As discussed above, the use of the true colors would most likely create a picture image that was less aesthetically pleasing than one “balanced for beauty”.
Unfortunately, those cameras do not allow an image to be captured without this processing; nor is it easy to reverse engineer this processing, as the algorithms and processing methods employed by the camera companies to so process their images are often maintained by the camera companies as trade secrets.
The goals of one performing a colorimetric analysis on a tissue sample are at odds with those desiring beautiful pictures. In order to make an appropriate colorimetric analysis of a color, it is important to be able to compare that color against a known standard, to help determine the differences between the color of a test subject and the color of the known standard. Additionally, if one is performing a colorimetric analysis on a large number of samples, to try to determine data relating to the comparative condition of the various samples, it is important to have the images of all of the test samples shot under generally identical conditions, so that differences in color reflect differences in actual tissue color, rather than reflecting differences in lighting, or color balance induced by the camera or its processor.
It is therefore one object of the present invention to provide a method and apparatus for facilitating the performance of a colorimetric analysis of a tissue sample by enabling the user to obtain a standardized color value of a patient tissue, that can then be used to better analyzing the condition of the patient. Preferably, this method can be performed with software and consumer affordable, commercially available hardware.